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e30 idle surge help! FIXED

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New to us, for my 16 yr old daughter.. 1987 325 2 dr. Automatic. 150k on the OD..

1987 325. Two door automatic..

It surges between 900 and 1500, but only after warmup.. Not uncommon, I guess. Runs like a top otherwise.

After cleaning the ICV didn't changed anything, remembering something about the other random things that can effect idle, I just casually pulled off the oil filler cap and BAM, it revved up, and then settled at about 1k..? Surge was gone!? So I pulled the valve cover and cleaned the vent, hose and TB. (Checked valve clearances while I was in there, just because.)

No change in the surge, unless I again pulled the filler cap.

Any suggestions, while I search bimmerforums?? I can't seem to find anything specific to this behavior..

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I have 87 325 2dr auto also. see my "saved another e30 today" thread in OT.

common m20 issue. tons of trouble shooting treads on this at r3vlimited.com, bimmerforums, etc.

vacuum leak..there are lots of place for this to happen.

ICV bad

ICM bad

leaking injectors (pull them and have them cleaned anyway. they need it.)

on these old cars, it is usually several things at once.

if you don't already have one, your first purchase should be a Bentley shop manual for car.

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I found a friend parting his rusted and folding DD, an '87 325e. Traded parts for ad space on my digital advertising screen at my coffee shop. His business is e30 motor swaps. Primarily shaved compartment s50 and s52.

Today I took the complete idle system. Air box. Cold start injector, BavAuto plug wires, fuse box and service plug covers. A fist full of other small bits that we needed, and the metal front valance to replace the rusty one on our car.

Later, I am getting the year old ST brand lowering springs, Konis, Ansa exhaust and e30 weaves, with centers.. I'm liking the e30 world so far.. LOL.

I swapped in everything in the idle system to no avail. Then found the CSI to be weeping. Swapped in the other, newer one, and BAM. the idle is no longer surging, and hovers at 800 rpm.

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